Abstract

Objectives: To characterize the phenotype of the
putative dendritic cells strongly expressing Jak3 and
STAT4, which have been previously identified in the
synovial tissue of patients with active Rheumatoid
Arthritis (RA).

Methods: Synovial biopsy specimens were obtained
at arthroscopy from 30 patients with active RA (42
synovial biopsies). Immunohistological analysis was
performed using monoclonal antibodies (Mab) to detect
dendritic cell subsets including activation markers as
well cytokines relevant to dendritic cell function. Co-
localisation of cell surface markers and cytokines was
assessed primarily using sequential sections, with
results confirmed by dual immunohistochemistry and
immunofluorescence with confocal microscopy.

Results:The dendritic cells identified in RA
synovial tissue which strongly express Jak3 also
strongly express STAT4 and STAT 6 and are correlated
with the presence of rheumatoid factor. These cells are
not confined to a single dendritic cell subset, with
cells having phenotypes consistent with both myeloid and
plasmacytoid type of dendritic cells. The activation
status of these dendritic cells suggests that they are
maturing or mature dendritic cells. These dendritic
cells produce IL-12 as well as Interferon á and ã.

Conclusions:The close correlation of these
dendritic cells with the presence of rheumatoid factor,
a prognostic factor for worse disease outcomes and the
strong expression by these cells of components of the
Jak/STAT transcription factor pathway suggest a
potential therapeutic target for the treatment of RA.

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